Rhodamine is a fluorescent dye known for many years similarly to fluorescein. Since both of these dyes show a high fluorescence quantum yield in water, they have been widely used in the field of biology as a fluorescent tag. Further, live cell imaging techniques utilizing a fluorescent probe have actively been used in recent years, and rhodamine is also frequently used as a parent compound for fluorescent probes that play an important role in such techniques.
As fluorescent probes having the rhodamine structure, there have so far been reported the probe for detecting nitrogen monoxide (International Patent Publication WO1999/001447), the probe for detecting hypochlorous acid (International Patent Publication WO2007/100061), and the like. Further, a compound corresponding to the basic structure of rhodamine, pyronin Y (PY), of which oxygen atom is replaced with silicon atom (TMDHS, 2,7-N,N,N′,N′-tetramethyl-9-dimethyl-10-hydro-9-silaanthracene) and application of this compound as a fluorescent probe have already been reported (Best, Q et al., Pacifichem 2010, subject number 2335, Dec. 19, 2010; Yuichiro KOIDE et al., Fourth Convention of The Japanese Society for Molecular Imaging, subject number P8-9, May 14, 2009).
The fluorescent probes having TMDHS as a basic structure are basically probes utilizing the intramolecular photoinduced electron transfer (PeT) or decyclization/cyclization of Spiro ring. However, in the compounds obtained by replacing the oxygen atom of PY with silicon atom reported so far, such as TMDHS, the amino groups of the 2-position and 7-position are substituted with substituents other than hydrogen atom such as methyl group. In addition, there have not so far been reported any rhodamine analogues corresponding to rhodamine having unsubstituted amino groups at the 3-position and 6-position (such a compound may be henceforth referred to as “N,N-unsubstituted 0 rhodamine” in this specification) of which oxygen atom is replaced with silicon atom, and also there has not so far been reported any fluorescent probes utilizing such a rhodamine analogue.